BIRMINGHAM, Ala. — The Mexican government is reviewing a labor union's complaint that Alabama's crackdown on illegal immigrants violates an international trade agreement.

An official with Mexico's labor department confirmed the review in a letter released Thursday by the group that filed the complaint, the Service Employees International Union.

The labor organization and a Mexican attorneys group filed a complaint in April. They contend Alabama's law targeting illegal immigrants violates protections guaranteed to migrant workers under a side agreement to the North American Free Trade Agreement, or NAFTA.

The Mexican government, in the letter, said it had asked the United States to begin talks allowed under the agreement.

Labor contends the state law, parts of which have been declared unconstitutional by federal courts, is discriminatory.

"We hope that further review of Alabama's racial profiling law will make clear its devastating impact on workers, on the law's potential for minimum wage and overtime violations, and on workers' freedom of association which are supposed to be protected under the NAFTA labor clause," Eliseo Medina, secretary-treasurer of the union, said in a statement.

A spokesman for Alabama Gov. Robert Bentley, Jeremy King, said the law tried to make sure people living in the state are doing so legally, "and there is nothing unjust about that."

The Republican Bentley signed HB 56, as it's known, into law last year, after it was passed by the GOP-controlled legislature. While intended to “put thousands of native Alabamians back in the work force,” the law instead led to a labor shortage. As a result, many Alabama farms have had little choice but to hire legal Haitian and African refugees to keep their businesses operating, Bloomberg reports.

The law has other problems as well. A federal appeals court in August struck down part of the law that ordered public schools to check the citizenship status of new students, but the court that also said police can demand proof of citizenship s from criminal suspects they detained.

The judges also sided with opponents of the law by striking down sections that made it illegal to harbor illegal immigrants; made it a crime for illegal immigrants to seek work; and made it a state crime for people in the country illegally not to have registration documents.